Load handling devices, especially heavy load carrying devices such as lift cranes and the like, are commonly provided with a turntable supporting a rotatable bed upon which upper works are mounted. Typically the upper works include inter alia a boom, a back hitch assembly, an equalizer assembly, rigging, and the load line as well as an offsetting counterweight. In the main, the forces created when lifting a load are offset by the action of the counterweight; however, the constant loading and unloading action creates tipping moments which must be absorbed by the turntable mechanism.
In the past attempts have been made to offset the tipping moments imparted to the rotatable bed as described above by utilizing load supporting rollers as well as hook rollers. One example of a rotatable bed with its corresponding roller assembly is more fully described in U.S. Pat. No. 3,989,325.